Refactor: Clear m_axObjectCache when AXObject detaches

Source/modules/accessibility/AXScrollbar.cpp

 /*
  * Copyright (C) 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 17 matching lines @@
 
 #include "config.h"
 #include "modules/accessibility/AXScrollbar.h"
 
 #include "modules/accessibility/AXObjectCacheImpl.h"
 #include "platform/scroll/ScrollableArea.h"
 #include "platform/scroll/Scrollbar.h"
 
 namespace blink {
 
-AXScrollbar::AXScrollbar(Scrollbar* scrollbar, AXObjectCacheImpl* axObjectCache)
+AXScrollbar::AXScrollbar(Scrollbar* scrollbar, AXObjectCacheImpl& axObjectCache)
     : AXMockObject(axObjectCache)
     , m_scrollbar(scrollbar)
 {
     ASSERT(scrollbar);
 }
 
 void AXScrollbar::detachFromParent()
 {
     m_scrollbar = nullptr;
     AXMockObject::detachFromParent();
 }
 
-PassRefPtr<AXScrollbar> AXScrollbar::create(Scrollbar* scrollbar, AXObjectCacheImpl* axObjectCache)
+PassRefPtr<AXScrollbar> AXScrollbar::create(Scrollbar* scrollbar, AXObjectCacheImpl& axObjectCache)
 {
     return adoptRef(new AXScrollbar(scrollbar, axObjectCache));
 }
 
 LayoutRect AXScrollbar::elementRect() const
 {
     if (!m_scrollbar)
         return LayoutRect();
 
     return LayoutRect(m_scrollbar->frameRect());
@@ skipping 43 matching lines @@
     if (!m_scrollbar->scrollableArea())
         return;
 
     float newValue = value * m_scrollbar->maximum();
 
     // TODO(bokan): This should potentially be a UserScroll.
     m_scrollbar->scrollableArea()->setScrollPositionSingleAxis(m_scrollbar->orientation(), newValue, ProgrammaticScroll);
 }
 
 } // namespace blink